Development model and experimental characterization of residual stress of 3D printing PLA parts with porous structure

Porous structural materials are widely adopted in medical field owing to their excellent mechanical and physical properties. The 3D printing technology offers new opportunities for the preparation of porous structures. However, during 3D printing of porous structure, continuous rapid heating and cooling cycles lead to residual stress. Severe quality defects including cracks, warpage, and deformation caused by the residual stress have remained to be a problem. In this study, a development model of residual stress with porous structure was established using fused deposition molding (FDM), and the residual stress was found to have a linear correlation with stress concentration coefficient. Samples with different pass and aperture sizes were fabricated by FDM. The residual stresses developed on the surface of samples were evaluated by Raman spectroscopy. The relationship between pore size and surface residual stress was obtained, indicating that the variation in surface residual stress is consistent with stress concentration coefficient with the increase in pore size. Based on above results, the accuracy of theoretical modeling was confirmed. This development model of residual stress has guiding paramount for 3D printing porous structures.